What can be seen here is a good example of a species which is slowly becoming extinct. The reason for this is, internally ventilated cast iron brake discs won't be around for much longer. Their parts are now being manufactured using lighter materials (among other things aluminium). Nevertheless, this is an nice piece of technology with interesting insides. It has several holes between the inner- and the outer disc which help the disc to cool down during the heat generation caused by the friction between pad and disc.
Basically, one differentiates between internally- and externally ventilated brake discs. In the case of the internally ventilated disc, displayed above, the cooling channels are radially arranged from the center outwards. The brake disc lies in an air-flow caused e,g., by guide plates mounted beside the front wheel, which direct the air-flow from the outside to the inside. In the case of the outside ventilated brake disc, the rotation of the disc itself, whose more slanting cooling channels take over the job of heat dissapation. 06/10